System for counterbalancing a tailgate

ABSTRACT

A counterbalancing system is provided that can be easily installed to an exterior of a tailgate and provides a mechanism for arresting the tailgate in an open position. The system includes a stop assembly coupled to the vehicle and a counterbalance assembly adapted to be coupled in a pretensioned position to an outer periphery of the tailgate, the counterbalance assembly providing a counterbalance force when engaged with the stop assembly while the tailgate is opened or closed.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/546,102, filed on Feb. 18, 2004 the entire teachings of that areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Typically, a tailgate is pivotally mounted between body side panelsforming the pillars at the rear of the vehicle. The tailgate pivotsabout a hinge axis between a horizontal, open position and a vertical,closed position. Preferably, the mounting assemblies for the tailgatepermit the tailgate to be removed, removal typically being accomplishedwhen the tailgate is pivoted to a position between the fully open orfully closed position. For example, the tailgate may include hinge pinsthat extend outwardly along the hinge axis that removably connect intobrackets carried on the truck body. When the tailgate is pivoted to apredetermined intermediate position, for example, 15° away from thefully closed position, at least one of the hinge pins slips through aslot in the connecting bracket as the tailgate is lifted at one end fromthe truck body.

Some of the tailgate mounting assemblies include counterbalancemechanisms, such as torque rods for assisting with the opening andclosing of the tailgate. These torque rods are located, at least inpart, within the tailgate for spring biasing between the tailgate andthe body panel pillars. These torque rods typically require numerouscomponents to assemble the torque rod to the tailgate.

In some instances, it may be desirable to keep the tailgate in the openposition, such as for transporting material having a greater length thanvehicle's bed. As such, the tailgate can be susceptible to closing byway of the counterbalancing mechanism. For example, the tailgate mightbounce in a direction toward closure if the vehicle were toinadvertently go over a bump or into a pothole, and the counterbalancingmechanism would then assist in potentially closing the tailgate.

SUMMARY OF THE INVENTION

The present invention provides a counterbalancing system that can beeasily installed to an exterior of a tailgate and provide a mechanismfor arresting the tailgate in an open position. The system includes astop assembly coupled to the vehicle and a counterbalance assemblyadapted to be coupled in an optional pretensioned position to an outerperiphery of the tailgate, the counterbalance assembly providing acounterbalance force when engaged with the stop assembly while thetailgate is opened or closed.

The stop assembly can be adapted to be coupled to an existing hinge pinof the vehicle. The stop assembly can include a semicircular groove forslidably engaging the counterbalance assembly.

The counterbalance assembly can include a spring member comprising afirst portion and a second portion that extends traversely from thefirst portion. The second portion can include a first notch positionedproximal to and below an end of the spring member for engaging the stopassembly and arresting the tailgate in a first position, wherein thefirst position can allow the tailgate to be arrested in a partiallyopened position. The second portion can further include a second notchpositioned proximal to and below the first notch for engaging the stopassembly and arresting the tailgate in a second position, wherein thesecond position can allow the tailgate to be arrested in a fully openedposition. The spring member can be a torque rod.

The stop assembly and the counterbalance assembly can be coupled as notto interfere with removal of the tailgate from the vehicle. The stopassembly and or the counterbalance assembly can be adapted to bespring-loaded for ease of installation of the tailgate to the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in that like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1A shows an exploded perspective view of a counterbalance assemblyof the present invention;

FIG. 1B shows an exploded perspective view a stop assembly of thepresent invention;

FIG. 2 shows a pretension angle “A” of a counterbalance assembly of FIG.1;

FIGS. 3A–3B illustrate installation of the present invention to atailgate of a vehicle;

FIG. 3C illustrates installation of the tailgate to the vehicle;

FIGS. 4A–4D illustrate the opening of the tailgate using the crank armof FIG. 2;

FIG. 5 shows another embodiment of a crank arm of the invention; and

FIGS. 6A–6D illustrate the opening of the tailgate using the crank armof FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

A description of preferred embodiments of the invention follows.

Generally, an externally mounted counterbalance mechanism is provided toassist with the opening and closing of a tailgate of a vehicle, such asa truck, minivan, station wagon, etc. The counterbalance mechanism canalso include a series of safety stops that arrest the tailgate inpredetermined positions.

FIG. 1A shows an exploded perspective view of a counterbalance assembly11 of the present invention. The counterbalance assembly 11 includes aspring member 12, a plurality of brackets (20, 22, 34), and bracketscrews (24, 26, 32, 40) for attaching the counterbalance assembly 11 toan exterior of the tailgate in an optional pretensioned position as willbe explained in further detail below. In one embodiment, the springmember 12 is a torque rod. The material used for the spring member 12should be chosen as not to fatigue as the spring member is rotated.

FIG. 1B shows an exploded perspective view of a stop assembly 13 of thepresent invention. The stop assembly 13 includes a stop bracket 44, astop pin 42, stop pin screws (46, 48), and bracket screws (52, 54) forattaching the stop assembly 13 to an existing hinge pin 50 on thevehicle. The stop bracket 44 includes an upper portion 62, a lowerportion 64, and an intermediate portion 60. The intermediate portion 60provides an offset between the upper portion 62 and the lower portion64. The stop pin 42 fastens to the upper portion 62 of the stop bracket44. As a result, the stop pin 42 can easily flex outward laterally, butis relatively rigid in the fore and aft direction. The stop pin 42includes a semicircular groove 56 facing forward and a tapered face 58facing backward. The semicircular groove 56 is positioned laterally tocradle a section of the spring member 12 (FIG. 1A) once the tailgate isinstalled. The semicircular groove can be replaced by a roller assembly,such as a one way roller.

FIG. 2 shows a pretension angle “A” of the counterbalance assembly 11.The spring member 12 is bent 90° to create a straight section 14 and acrank arm 16. Typically, a length of the straight section 14 is greaterthan a length of the crank arm 16. The straight section 14 includes aflat portion 30 that is disposed at an angle “A” (zero torque position)relative to a center axis of the crank arm 16, typically in the range of60°. Bracket 22 includes a flat surface 28 for mating with the flatsurface 30 of the straight section 14 such that free rotation of thecounterbalance assembly 11 is prevented. Bracket 34 includes a lip 36for holding the spring member 12 in a pretensioned position as describedin further detail below. Pretensioning of the counterbalance assembly 11is optional and provides for a greater restoring force than that of anassembly having no pretension.

FIGS. 3A–3B illustrate the installation of the spring member 12 of thepreceding figures. Brackets 20, 22 are attached to the bottom 8 of atailgate 18 and bracket 34 is attached to a side 38 of the tailgate. Thelip 36 of the bracket 34 should be on an edge inward toward a bed of avehicle. Once the brackets 22, 24, 34 have been installed, the springmember 12 is inserted into brackets 20, 22 with the flat portion 30 ofthe straight section 14 aligned to fit into the respective flat matingsurface 28 of the bracket 22 until the crank arm 16 hits the side 38 ofthe tailgate 18 as shown in FIG. 3A. The spring member 12 can freelyslide in and out of the brackets 20, 22, but cannot rotate once thespring member 12 is engage with bracket 22.

The crank arm 16 can then be forced in a counterclockwise directionrelative to FIGS. 3A and 3B until it clears the top of the lip 36 on theretaining bracket 34. At that time, the spring member 12 can be fullyinserted into bracket 22 and secured with screw 32, as shown in FIG. 3B.The rotation of the crank arm 16 reduces angle “A” (FIG. 2) toapproximately 0°. This reduction creates an amount of torque on thespring member 12 that left unrestrained by the lip 36 would restore thespring member 12 to its normal or zero torque position. Although thestraight section 14 of the spring member 12 is shown across the entirelength of the tailgate 18, it should be understood the length of thestraight section 14 can be any length that provides a sufficientrestoring force.

FIG. 3C shows a cutaway view of the tailgate 18 mounted to a vehicle 10.The tailgate 18 of FIGS. 3A and 3B is rotated to align with the vehicle10 as shown. The stop assembly 13 can be mounted to an existing hingepin 50 located on the vehicle 10. It should be understood that thetailgate 18 is mounted to the vehicle 10 in the conventional manner asknown in the art. Installation of the tailgate 18 is described withreference to the preceding figures. First, a first trunnion 66 (FIG. 3B)can be inserted over a respective hinge pin 50 on a body of the vehicle10, and while holding the tailgate 18 at an approximately 45° slant, asecond trunnion (not shown) can slid over a slanted hinge pin (notshown), at that point the tailgate 18 can be closed.

In some instances, the stop pin 42 can obstruct the crank arm 16 as thetailgate 18 is lifted, but by virtue of its tapered face 58 (FIG. 1B)the stop bracket 44 and the crank arm 16 flex laterally out and in,respectively, to allow the crank arm 16 to pass into position. Once thecrank arm 16 is past the stop pin 42, the stop bracket 44 and the crankarm 16 spring back into position laterally, and the crank arm 16 iscaptured by the groove 56 (FIG. 1B) of the stop pin 42. It should berealized that the flexing action described above is merely a conveniencefeature during the installation of the tailgate 18. The operation of thepresent invention would remain unchanged if the stop bracket 44 wererigid. Thus, the operator would merely be forced to hold the tailgate 18straight up and down as he engages the first hinge pin, then lower itapproximately 45 degrees to engage the second hinge pin.

FIGS. 4A–4D illustrate the opening of the tailgate 18 using the crankarm 16 of FIG. 2. The viewing angle of this illustration is lookingthrough the near side of the vehicle 10 (FIG. 3C) in the direction ofthe hinge pin 50. The stop pin 42 is attached to the vehicle 10 and isstationary relative to movement of the tailgate 18.

FIG. 4A shows the tailgate 18 in a closed position with the crank arm 16remaining in the pretensioned position by the lip 36 of the bracket 34.There is approximately 15° of free travel of the tailgate 18 between theclosed position and engagement of the spring member 12 and the stop pin42. In this position the opening gravitational moment acting on thetailgate is very slight and the pretensioning of the torsion rod can bechosen to exceed it easily such that the tailgate is arrested in a“safety stop” position. As shown in FIG. 4B, the tailgate is engagedwith the crank arm 16. Once the spring member 12 and the stop pin 42 areengaged, a counterbalance force or restoring force is applied to thetailgate 18 to assist an operator with either opening or closing thetailgate 18. That is, the spring member 12 tries to restore itself tothe normal position as shown in FIG. 2. As the tailgate 18 is loweredfurther as shown in FIG. 4C, the amount of restoring force on the springmember 12 increases since the spring member 12 is rotated further fromits normal position. The tailgate 18 is then dropped to the fully openposition shown in FIG. 4D. At this point the amount of restoring forceon the spring member 12 is greatest since the spring member 12 isrotated furthest from its normal position.

FIG. 5 shows another embodiment of the crank arm 16 of the precedingfigures. The crank arm 16′ is shaped to include two curved notches “B”and “D” and a curved section “C” for arresting or locking the tailgate18 in predetermined positions as explained with reference to FIGS.6A–6D. The notches “B” and “D” prevent the tailgate from inadvertentclosure. It should be understood that any number of notches or curvescan be used to arrest the tailgate in a predetermined position. Further,the deeper the notches the more force is required to move the tailgatefrom the predetermined position.

FIGS. 6A–6D illustrate the opening of the tailgate 18 using the crankarm 16′ of FIG. 5. The viewing angle of this illustration is the same asthe viewing angle as described with reference to FIGS. 4A–4D. FIG. 6Ashows the tailgate 18 in a closed position with the crank arm 16′remaining in the pretensioned position by the lip 36 of bracket 34.There is approximately 15° of free travel of the tailgate 18 between theclosed position and engagement of the spring member 12 and the stop pin42. Once the spring member 12 and the stop pin 42 are engaged, acounterbalance force or restoring force is applied to the tailgate 18 toassist an operator with either opening or closing the tailgate 18. Inthis position the opening gravitational moment acting on the tailgate isvery slight and the pre tensioning of the torsion rod can be chosen toexceed it easily such that tailgate is arrested in a “safety stop”position. As shown in FIG. 6B, the tailgate is held or locked in a“safety stop” or arrested position once the stop pin 42 engages notch“B” of the crank arm 16′. The notch “B” further enhances arresting thedrop of the tailgate. The notch “B” of the crank arm 16′ can be eitherstraight or curved as shown. The curvature makes it possible to bettercounterbalance the sinusoidal gravitational pull by the linearstress-strain characteristic of the spring member 12. To lower thetailgate beyond this point requires the operator to pull the tailgate 18in a downward direction past notch “B” as shown in FIG. 6C. The amountof restoring force on the spring member 12 increases since the springmember 12 is rotated further from its normal position. The tailgate 18can then be dropped to the fully open position shown in FIG. 6D as thenotch “D” of the crank arm 16′ engages the stop pin 42. At this pointthe amount of restoring force on the spring member 12 is greatest sincethe spring member 12 is rotated furthest from its normal position. Thedepth of the notch “D” determines how firmly the tailgate is restrainedin the open position, such as to prevent an inadvertent closure of thetailgate.

As an additional feature to cushion the drop of the tailgate, thesliding action of the crank arm 16 can be utilized to push against aviscous damper mounted on the truck just above the stop pin 42 (notshown).

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims. For example, the crank arm mayterminate in a laterally positioned pin that rides up and down over ashaped cam surface mounted to the truck. Although the counterbalanceassembly is shown to be in a pretension position, it should beunderstood that pretension is not necessary to provide thecounterbalancing means.

1. A system for counterbalancing a tailgate of a vehicle, comprising: astop assembly coupled to the vehicle; and a counterbalance assemblyadapted to be coupled in a pretensioned position to an outer peripheryof the tailgate, the counterbalance assembly providing a counterbalanceforce when engaged with the stop assembly while the tailgate is openedor closed and the counterbalance assembly, prior to engagement with thestop assembly, allowing for motion, without the counterbalance force,between closed and partially opened positions.
 2. The system of claim 1,wherein the stop assembly is adapted to be coupled to an existing hingepin of the vehicle.
 3. The system of claim 1, wherein the stop assemblyincludes a semicircular groove for slidably engaging the counterbalanceassembly.
 4. The system of claim 1, wherein the stop assembly and thecounterbalance assembly are coupled as not to interfere with removal ofthe tailgate from the vehicle.
 5. The system of claim 1, wherein thestop assembly and the counterbalance assembly are adapted to bespring-loaded for ease of installation of the tailgate to the vehicle.6. The system of claim 1, wherein the stop assembly or thecounterbalance assembly is adapted to be spring-loaded for ease ofinstallation of the tailgate to the vehicle.
 7. The system of claim 1,wherein the counterbalance assembly includes a spring member comprisinga first portion and a second portion that extends transversely from thefirst portion.
 8. The system of claim 7, wherein the spring member is atorque rod.
 9. A method of assembling a counterbalancing system for atailgate of a vehicle, comprising: coupling a stop assembly to thevehicle; and coupling a counterbalance assembly adapted in apretensioned position to an outer periphery of the tailgate, thecounterbalance assembly providing a counterbalance force when engagedwith the stop assembly while the tailgate is opened or closed and thecounterbalance assembly, prior to engagement with the stop assembly,allowing for motion, without the counterbalance force, between closedand partially opened positions.
 10. The method of claim 9, wherein thestop assembly is adapted to be coupled to an existing hinge pin of thevehicle.
 11. The method of claim 9, wherein the stop assembly includes asemicircular groove for slidably engaging the counterbalance assembly.12. The method of claim 9, wherein the stop assembly and thecounterbalance assembly are coupled as not to interfere with removal ofthe tailgate from the vehicle.
 13. The system of claim 9, wherein thestop assembly and the counterbalance assembly are adapted to bespring-loaded for ease of installation of the tailgate to the vehicle.14. The system of claim 9, wherein the stop assembly or thecounterbalance assembly is adapted to be spring-loaded for ease ofinstallation of the tailgate to the vehicle.
 15. The method of claim 9,wherein the counterbalance assembly includes a spring member comprisinga first portion and a second portion that extends transversely from thefirst portion.
 16. The method of claim 15, wherein the spring member isa torque rod.
 17. A system for counterbalancing a tailgate of a vehicle,comprising: a stop assembly coupled to the vehicle; and a counterbalanceassembly adapted to be coupled in a pretensioned position to an outerperiphery of the tailgate, the counterbalance assembly providing acounterbalance force when engaged with the stop assembly while thetailgate is opened or closed, the counterbalance assembly including aspring member comprising a first portion and a second portion thatextends transversely from the first portion, and the second portionincluding a first notch positioned proximal to and below an end of thespring member for engaging the stop assembly and arresting the tailgatein a first position.
 18. The system of claim 17, wherein the firstposition allows the tailgate to be arrested in a partially openedposition.
 19. The system of claim 17, wherein the second portionincludes a second notch positioned proximal to and below the first notchfor engaging the stop assembly and arresting the tailgate in a secondposition.
 20. The system of claim 19, wherein the second position allowsthe tailgate to be arrested in a fully opened position.
 21. A method ofassembling a counterbalancing system for a tailgate of a vehicle,comprising: coupling a stop assembly to the vehicle; and coupling acounterbalance assembly adapted in a pretensioned position to an outerperiphery of the tailgate, the counterbalance assembly providing acounterbalance force when engaged with the stop assembly while thetailgate is opened or closed, the counterbalance assembly including aspring member comprising a first portion and a second portion thatextends transversely from the first portion, and the second portionincluding a first notch positioned proximal to and below an end of thespring member for engaging the stop assembly and arresting the tailgatein a first position.
 22. The method of claim 21, wherein the firstposition allows the tailgate to be arrested in a partially openedposition.
 23. The method of claim 21, wherein the second portionincludes a second notch positioned proximal to and below the first notchfor engaging the stop assembly and arresting the tailgate in a secondposition.
 24. The method of claim 23, wherein the second position allowsthe tailgate to be arrested in a fully opened position.
 25. A system forcounterbalancing a tailgate of a vehicle, comprising: means for couplinga stop assembly to the vehicle; and means for coupling a counterbalanceassembly adapted in a pretensioned position to an outer periphery of thetailgate, the counterbalance assembly providing a counterbalance forcewhen engaged with the stop assembly while the tailgate is opened orclosed and the counterbalance assembly, prior to engagement with thestop assembly, allowing for motion, without the counterbalance force,between closed and partially opened positions.
 26. A system forcounterbalancing a tailgate of a vehicle, comprising: a stop assemblycoupled to the vehicle; and a counterbalance assembly adapted to becoupled to an outer periphery of the tailgate, the counterbalanceassembly providing a counterbalance force when engaged with the stopassembly while the tailgate is opened or closed and the counterbalanceassembly, prior to engagement with the stop assembly, allowing formotion, without the counterbalance force, between closed and partiallyopened positions.